Stabilizing Ni-Co Alloy on Bimodal Mesoporous Alumina to Enhance Carbon Resistance for Dry Reforming of Methane
Bin Li, Bin Li, Xiaoqing Yuan, Lvyin Li, Xiujun Wang, Baitao Li, Baitao Li
Abstract
Alloying nickel with a transition metal and further stabilizing an active metal on bimodal support are regarded as a promising strategy to improve carbon resistance for dry reforming of methane (DRM) reaction. In this work, a bimodal mesoporous alumina-supported Ni-Co alloy catalyst (NiCo/MMAl) was prepared via the evaporation-induced self-assembly method and employed to catalyze DRM reaction. The promotive effect of Ni-Co alloy with a bimodal porous structure on the carbon resistance was investigated. The presence of Ni-Co alloy was confirmed on porous alumina. The NiCo/MMAl catalyst possessed two porous structures, a small-sized mesopore at 10 nm and a large-sized one at 40 nm. NiCo/MMAl exhibited enhanced carbon resistance, in which only 2.3% carbon formed on the catalyst surface, lower than a unimodal mesoporous alumina-supported NiCo catalyst (NiCo/MAl, 12%) and Ni catalyst (Ni/MAl, 24%). The kinetic study suggested that on the unimodal mesoporous alumina, alloying Ni with Co increased the activation energy of CH4 dissociation (∼66 kJ/mol) compared to Ni/MAl (51.7 kJ/mol), thus showing high activity for suppressing CH4 dissociation. In addition, the large-sized mesoporous structure on NiCo/MMAl favored mass transport. As a result, the enhanced carbon resistance for NiCo/MMAl was not only attributed to the suppression of CH4 dissociation by Ni-Co alloy but also to the promotive effect of the large-sized mesopore structure on enhancing mass transport.